Smart has created the first derivation of its Fortwo and Forfour city cars. Unsurprisingly, this is the latest example of a vehicle we've seen before - the Smart Cabrio.

What are the highlights of this new open-top?

You get three machines in one: a closed two-seater with the roof, er... closed; a car with a full-length fabric sunroof if you just open the top on the horizontal plane; and then the total Cabrio experience with the roof folded back to its fullest; thus Smart calls it the 'tritop'. Doing the full Monty takes just 12 seconds and can be carried out on the move - right up to the Smart's maximum speed of 96mph. Use the newly designed ignition key and the tritop can be lowered remotely from outside the Cabrio too.

I can see roof bars in the picture - what are they about?

If you want the widest aperture possible above your head, then you can pop these out of the Cabrio's Tridion safety cell and store them in the boot, where there's a special compartment for them.

Does the roof come in some funky colours?

Red, black or 'jeans look' denim blue. Whichever one you choose, the headlining within will be grey. On a connected note, the removable roof bars are finished in whatever hue buyers choose for the Tridion cell.

What about engines?

The same three-cylinder petrol pair as from the Fortwo and Forfour line-ups - a 1.0-litre normally aspirated engine with 71hp and 91Nm, or a 0.9-litre turbocharged unit with 90hp and 135Nm. Either comes with the five-speed manual as standard or the Twinamic dual-clutch as an option auto (a fine transmission that banishes memories of the dreadful old gearboxes of early Smarts). Plumping for the latter lengthens 0-62mph times (range-wide, they run from 10.8 seconds in the 90hp manual to 15.5 seconds for the 71hp Twinamic), but doesn't affect the cars' top speeds of 94mph (71hp) and 96mph (90hp) respectively. The 90hp Twinamic is slightly greener than the manual example, though, at 67.3mpg and 97g/km CO2 emissions, compared to 65.7mpg and 99g/km. Either example of the 1.0-litre Cabrio matches those latter two economy/CO2 figures.

Is it safe?

Yes, extra reinforcements on the underside of the chassis, in the form of two torsional bulkheads and with tubes of high-strength steel incorporated into the A-pillars means the Smart has passed all the rigorous safety tests required of it - and it's 15 per cent stiffer than its predecessor. Electronic safety gadgets (both standard-fit and optional) include Crosswind Assist, Hill Start Assist, Forward Collision Warning and Lane Keeping Assist. The Cabrio should also be comfortable, as the 20mm-thick tritop has a rubber layer sandwiched in the middle of it and a wind deflector is an option for the cabin.

Can you tell me about prices and first deliveries?

The same trim lines of Passion, Prime and Proxy are retained for the Cabrio, although we can't tell you a price as yet - budget on it being quite a bit more than the already robust starting price of £11,125 for a Fortwo Passion 71hp manual. Following its debut at the Frankfurt Motor Show next month, the Smart Cabrio order books will open mid-November, ahead of the first cars reaching dealers in February 2016.